Relative tolerance of photosystem ii in spike, leaf, and stem of bread and durum wheat under desiccation

In dryland regions, soil moisture stress often leads to desiccation and causes injury to photosynthetic machinery. Recently, chlorophyll fluorescence (ChlF)-based assessment of photosynthetic efficiency under drought stress is gaining attention due to advances in instrument development and methodology optimisation. Our study was designed to explore the use of spike photosynthetic efficiency as a trait to differentiate drought responses in wheat. Bread and durum wheat were assessed for spike, stem, and leaf tissue photosynthetic efficiency in response to progressive desiccation using ChlF imaging. Results showed that durum wheat had higher quantum efficiency and lower photoinhibition of PSII relative to bread wheat across spike, stem, and leaf. Rate of decline in maximum photochemical efficiency of PSII with increased desiccation was seen higher in bread wheat spikes as compared to durum wheat. Our investigation clearly demonstrated that ChlF imaging could be effectively deployed as phenotyping tool to differentiate wheat genotypes for their photosynthetic performance under desiccation.